Mechanical fluid dynamic device for the propulsion and flow control in the water-jet propelled boats

ABSTRACT

The device includes conveying ducts of the fluid ( 2, 9 ), a tubular mean ( 1 ) with variable internal volume ( 1 ′), a tapered onion-shaped body ( 17 ) centred ( 18 ) inside the tubular mean, a nozzle ( 16 ) for the ejection of the fluid adjustable in position and opening for the variation of said internal volume ( 11 ), one or more gas injectors ( 21 ), and means to change the direction of the jet ( 6 ). In this way a fluid with variable characteristics can be obtained which allows the adjustment of the intensity, flow, direction and slant of the jet ( 6 ), moreover releasable also above the water surface ( 10 ), in view of the optimisation of the increased performances and consumption reduction. Unlike the devices of the known technique suitable only to convey the fluid and give the flow a single direction, the jet ( 6 ) is not diverted by other members, but is oriented through the joint ( 8 ) which allows its displacement in all the directions, in fact thanks to this said jet ( 6 ) can be directed without damping. It finds peculiar application in the propulsion and control of the hydrodynamic flow in the water-jet propelled boats or craft, besides as retrofit of easy embodiment to be installed also on the boats that have a traditional water-jet.

The subject of this invention is an integrated mechanical fluid dynamicdevice or unit to be coupled to a traditional boat water-jet, able tointeract with the some jet and to modify all the characteristics of thesaid hydraulic flow, obtaining a water-jet controlled and adjusted inthrust and direction, with advantage to the best speed and consumptionperformances.

Currently and usually the water-jet propulsion units are not able or arenot intended to control and adjust the parameters of the flow whichdetermines the thrust, in fact, they are suitable only to convey thefluid and give the flow a single direction, according to the amount ofpumped water, furthermore all the traditional water-jets utilise thepumping system with underwater release of the hydraulic flow under thesurface of the water or at a level that from the start until the phaseof planning remains immersed and disturbed by the ebb of the wake,contrary to this invention where the jet is expelled still at thebeginning outside of the surface of the water.

Some water-jet propulsion devices have tried to intervene on the fluxparameters through variation of volume, shape and direction of thenozzle by means of mobile surfaces or creating a poly-phase fluid,water-gas, but at expense of complicated mechanism mostly of complexcarrying out and mostly expensive.

The propulsion unit, subject of this invention, unlike those of theknown technique, allows essentially to adjust and control thecharacteristics of the flow and the pumped water jet, like density,speed, angle of incidence, direction, by variation of the motion amongits internal components or movement of the whole unit, while in thetraditional water-jets nothing of that happens, in fact they convey andeject the pumped water by variation of the shape of the walls or theirrotation.

As far as the applicant knows in fact up to today the devices of theknown technique do not allow the variation of the characteristics of thejet in this way.

In fact making reference of the next State-of-the-Art, the U.S. Pat. No.5,692,371 shows a ram-jet engine where the change of the internal volumeof the chamber and the orientation of the jet occur by variation of therelative position of the mobile foldable walls of the nozzle,kinematical adjustable bodies in its interior and rotation of a part ofits walls, and neither by displacement of the nozzle or of thehydrodynamic body in the chamber nor by its rotation, all methods anddevices that are detrimental to the efficiency of the jet.

The USA Patent Application 2003/0013356 presents a propulsion devicewith morphological characteristics similar to the above mentioned patentfor the control of the flow and to operate it needs a three-phasedsystem of liquid, that is it is based on a working principle fullydifferent from that of this invention.

In fact the intake of the gas is in our case only functional to thevariation and control of the characteristics of the jet, to increase itsperformance and complementary to its power, no to produce the main powerof the jet.

In both cases the injection of the gas into the tubular chamber thatgenerates the power occurs in a chaotic and aleatory way with reducedefficiency because of the increase of the pressure drops of the nozzle,while in our case the injection of the gas drawn from the internalcombustion engine driving the hydro pump, that creates ad feeds the jet,has on the contrary the aim of complement to increase the efficiency andfurther control the flow. In fact it is released in a precise point atthe middle of the ring element so that it laps against the whole surfaceof the onion or pinecone-shaped body, said gas, or alternativelycompressed air, having a density lower than that of the water and ahigher speed, reduces decidedly the friction between water and surfaceof the tubular onion or pinecone-shaped body so that it favours thefluency and increase at the same time the speed of the flow, lowering atthe same time the pressure drops.

On the contrary the subject of this invention, by the adoption of thedevice as described and depicted in the following, allows through avariable volume directional chamber to increase the jet speed besidesits angle of incidence, while the density is changed by the introductionof gas, for example the exhaust of the engine, into the same chamber,finally the kinetic energy of the jet is increased by the jet ejectionabove the surface of the water, and also by the effect of the said gasinjection that in our case is not chaotic but circumscribed around thetubular body centred inside the chamber, with an adjustable slant whichcharacterises the boat attitude.

That is the main difference from the methods of the known State of theArt, the subject device or unit bringing instead a considerable increaseof the performance, both about speed and agility/handling. Especially inthe phase of start and acceleration, in fact such system is able to makeup for the drawbacks of the traditional water-jets, that in the startphase until the attainment of the plane, or at low speeds when the craftdoes not plane, give cause to an excessive consumption, caused mainly bythe fact that the thrust energy given by the mass times the speedsquared is higher in our system as consequence of the fact that we couldincrease the speed of the flow first allowing it to flux to open air,which has a noticeably lower density, and secondly imposing by a limitedcontrol an easier downflow of the fluid on the internal tubular bodywith injection of gas or compressed air.

In any case the jet results already by itself exceptional and efficient,also without the injection of gas or compressed air, because of thevariation of its flow and direction.

More in detail, unlike the devices of the known technique, the presentinvention refers precisely to a mechanical fluid dynamic jet device forthe propulsion and control of the hydrodynamic flow in the water-jetpropelled boats, including conveying ducts of the fluid, a tubular meanwith variable geometry and variable internal volumes, a body centredinside said tubular mean by means of a ring of wing aerodynamic sectionor a ring nut carrying spokes or fluid dynamic blades, an adjustablenozzle to eject the fluid, one or more gas injectors, and means tochange the direction and the slant of the jet, characterised by the factthat the variation of volume of the internal chamber of the tubular meanfor the flow control is obtained by displacement and opening of theadjustable nozzle to change said internal volume, without the need ofvariation of the shape and geometry of said nozzle.

Said mechanical fluid dynamic jet device for the propulsion and controlof the hydrodynamic flow in the water-jet propelled boats, isfurthermore characterised by the fact that the variation of the volumeof the chamber inside the tubular mean for the control of the flow isobtained by displacement of the adjustable nozzle from a position ofminimum opening to one of maximum opening.

Said mechanical fluid dynamic jet device for the propulsion and controlof the hydrodynamic flow in the water-jet propelled boats, isfurthermore characterised by the fact that the movement of the nozzlefor the adjustment of the volume of the chamber inside the tubular meanis carried out by a motorised system including an electrical steppermotor and by a gearbox, pinion and cogwheel, or by a hydraulic actuationdevice, suitable to displacement, adjustment and restriction of the saidnozzle from a minimum to a maximum opening position for the variation ofthe kinetic energy of the jet itself.

The device of the invention characterises itself also by including ahydrodynamic body for the guidance and the control of the flow insidethe tapered onion-shaped chamber and by the fact that it is centredfixed inside the said tubular mean a wing-shaped ring or a ring nutcarrying spokes or fluid dynamic blades.

In the mechanical fluid dynamic jet device for the propulsion and thecontrol of the hydrodynamic flow in the water-jet propelled boats thetapered pinecone or onion-shaped body for guidance and control of theflow is of elastic deformable material and includes a hole connected toan hydraulic circuit to be filled with fluid to change its volume toobtain a further adjustable element to control the hydrodynamic flow.

So that the flow can be controlled also by the hydraulic swelling of thetapered onion of elastic polymeric material without resort to mobilesurfaces or complex mechanisms, drawback from the point of view of theircarrying out, cost and reliability.

Furthermore in the mechanical fluid dynamic jet device for thepropulsion and control of the hydrodynamic flow in the water-jetpropelled boats, the ring or nut, on which the hydrodynamic pinecone oronion-shaped body is mounted and centred to drive and control thehydrodynamic flow inside the tubular mean, is a wing section oraerodynamic profile, and is mobile translating along the axis of thesaid body from a point of minimum to a point of maximum to determine afurther adjustable element to change the flow parameters. Said elementis able to create with its wing profile, concentric to the aerodynamicbody, a depression centred in the chamber on the said onion-shapedtubular body and is essential to arrange for the air or the gas beingdriven by this depression to lap only on said tubular body, in order toassure an increase of the speed of the jet which is determined by thebetter fluency due to the lower sliding friction of the water on theonion.

The mechanical fluid dynamic jet device for the propulsion and controlof the hydrodynamic flow in the water-jet propelled boats includes alsoinjectors that are placed and arranged in the middle of the wing-shapedring to force the gas to lap only on the surface of the pinecone withoutdisperse in the chamber, so that reduces the frictions between water andsurface of the pinecone and at the same time increases the speed of thejet.

This, while the gas injection is carried out by means of injectorscommunicating with the interior of the tubular mean, in order to changethe main characteristics of the jet, like speed and density, besides theperformances, power and angle of incidence, of said jet together withthe adjustment of the volume of the chamber, with the consequentialvariation of the kinetic energy of the jet itself, said gas could becomposed by the exhaust extracted from the engine or by a compressed aircoming from a tank with release and control valve, connected to aturbocharger, driven by the same engine of the boat.

The device of the invention allows in addition the variation of thedirection and the slant of the jet, course and attitude of the boat,through means formed by a jointed system, suitable to orient saidtubular body mounted on said joint in direction and slant, which allowsthe displacement of the device in all the directions, without the needof displacement of mobile surfaces in the manner of rudders that dampthe jet.

By means of this device the jet, besides the possibility of a releaseunderwater like the traditional water-jet, can be also released outsidethe water above the water surface, like a jet engine or water-jet, saidoption resulting more effective and more appreciable in terms of betterperformances. Particularly the response at low speeds must be noted,while by the traditional water-jets at low speeds, that is when the boatis not yet about to plane, the engine consumes as much as at highspeeds, this defect which remains still a handicap in the traditionalboats is instead remarkably solved by this invention.

The mechanical fluid dynamic jet device for the propulsion and controlof the hydrodynamic flow in the water-jet propelled boats finds also usein the hydrodynamic guidance and control of the boats when it issymmetrically arranged in a given number of couples on the lateral wallsof the hull to optimise the auxiliary manoeuvres in harbour, saidnozzles fed by hydraulic pumps by means of shutters driven byelectrovalves and controlled by joystick.

The mechanical fluid dynamic jet device finds particular use to controlthe hydrodynamic flow in the propulsion and in the manoeuvre ofwater-jet propelled boats or crafts.

In addition said device, besides the installation “ex novo” on the boatsor craft intended for the water-jet propulsion, allows retrofit actionson the boats of the known technique, because it can be easily installedalso on the boats which have a traditional water-jet.

The unique innovative element which justifies our patent applicationconsists of having a water-jet with nozzle adjustable through amechanism driven by a stepper motor, guaranteeing in this way thepossibility to change the volume of the chamber for the control of thepower of the jet without modification of the geometry and shape of thenozzle with multiplied hydrodynamic efficiency and high constructionreliability avoiding mobile surfaces.

Carefully studying the above mentioned documents of the previous Stateof the Art, it is evident that in none of them, unlike this invention,the fact appears that said water-jet is purposely built and designed tooperate outside the water surface, as well as the fact that in thisinvention, unlike the others, to make the boat turning rudder or mobilesurfaces are not needed to deviate the jet, configurations that damp theflow deviating it, but it is able to rotate the whole jet without takingpower out.

It is to be added that in this invention we adopt an hydrodynamic bodyinside the variable chamber shaped as deformable tapered pinecone oronion, to change its shape and volume, which determines in theinteraction with the flows new characteristics that cause an incrementof kinetic energy of the flow, higher incisiveness, better performancefor the boat, being a further adjustable element of control.

Similarly the nut supporting said hydrodynamic body is shaped like aring with wing section able to create a depression at the centre justaround the hydrodynamic body, causing an increase of the speed of theflow, allowing to use a very tapered pinecone shape instead a morepronounced onion shape as usual, therefore without inducing excessiverestriction of the flow which would loose more energy, obtaining abetter result without restriction of the chamber, but utilising the saidelement.

Currently in the traditional systems quoted before the speed of thepumped fluid is increased by means of the onion or pinecone-shapedelement at the centre of the duct where the fluid flows, in all thesecases to obtain a satisfactory result restrictions are practicallycarried out that in any cause take power away the flow with pressuredrops, in our case, even noticeably reducing the restrictions imposed bythe onion which results more slender with the application of the specialring which support it around itself, we obtain better results in termsof power essentially because we have reduced the pressure drops.

Furthermore bear in mind that the ring can be mobile, transferringlongitudinally, becoming a further adjustable element of control toimprove the propulsion device and to refine the efficiency.

Said ring sliding along the axis of the pinecone, remaining centredagainst it, bring by this effect a change of the flow inside the chambercausing an element of further implementation in the control.

About the carrying out of the jet by a bi-phase flow liquid-gas, thedouble flow air or gas plus water, pre-eminent to give power to the jetin the previous technique, in our case drawn from the power generator,internal combustion engine or turbine, it is only complementary toincrease the power, increasing on the contrary the efficiency and thepossibility of control of the flow. The injection occurs at the centreof the wing-shaped ring, which is able through the depression creativeat its centre to force the gas to lap the surface of the pineconeavoiding actually that the same gas flows freely in the whole chamber,this element because of its deployment in that specific position andwith that particular section in fact succeeds to drive, concentrate andmake the gas lapping only on the pinecone.

The fluid dynamic mechanical jet device subject of this invention findsfurther use for the control of the aerodynamic flow in the propulsionand the manoeuvre of the water-jet propelled boats and craft and asretrofit of easy embodiment to be applied also on the boats that have awater-jet or manoeuvre propellers of traditional type.

We give now in the following a description of a particular non-limitingform of carrying out of the invention without depriving of anything thegenerality of the invention itself and without limiting the field ofimplementation, with reference to the explanatory drawings of theattached tables.

FIG. 1 shows a view of the device as applied to a water-jet propelledboat.

FIG. 2 shows a view more in detail of the table 1 indicating also theflows and the movements of the device.

FIG. 3 shows a cross section of the body and the tubular chamber, thenozzle and the joint of the device of the invention.

FIG. 4 shows the pinecone or onion-shaped hydrodynamic body installedinside the chamber, provided with internal hole to change its shape andvolume.

FIG. 5 shows the mobile wing-shaped ring element acting as support andcentring nut of the pinecone or onion-shaped hydrodynamic body.

FIG. 6 shows an installation arrangement of a couple of water-jets withauxiliary manoeuvre function at the boat prow.

FIG. 7 shows an installation arrangement of the water-jets, withauxiliary manoeuvre function, on the hull of the boat, prow and stern,for its guidance in the manoeuvres in harbour, of sailing and docking.

A motor or pump 4 through the intake 3, 25 of a boat 5, 11 takes andconveys the fluid in the duct 2 and in the subsequent duct 9 up to theinside 1′ of the tubular chamber 1, where the flow is managed,controlled and adjusted and subsequently ejected and transformed in jet6 through the nozzle 16, preferably above the water surface 10 (FIGS. 1,2).

The flexible or rigid ducts 2, 9, can be made of any material compliantto the requirement of watertight and mechanical resistance, suitable toconnect the pump 25, 3 to the control and propulsion device 21, 8, 1, 16(FIG. 2).

The pumped fluid can be altered as one likes in its characteristics bythe concomitant introduction of gas taken from the engine exhaust 4through the duct 2 a or alternatively from a compressed air tank andinjected through the control valve 26 by means of one or more injectors21 into the duct 2 (table 2) in a preferred form of manufacture of thisinvention or into the chamber 1′ of the tubular body 1 (FIG. 3) in asecond preferred form of manufacture.

Said fluid comes into the internal chamber 1′ of the tubular body 1,driven and regularised by a tapered onion-shaped hydrodynamic body 17intended to regularise the flow, centred inside said chamber 1′ by meansof a ring or clamp 18 carrying the onion-shaped body with fluid dynamicblades and ledges 19, 20 (FIG. 3).

Similarly a nozzle 16, actuated and adjusted from a minimum to a maximumopening position by means of a cogwheel 15 and a pinion 13, driven by anelectrical stepper motor 12, 24, 14, allows the variation of theinternal volume 1′ of the tubular chamber 1 (FIG. 3).

Said device works like a hydro-jet, including a tubular body 1, with aninternal variable geometry and volume chamber 1′, a tapered onion-shapedelement 17, arranged longitudinally to the flow, fixed 23, 19, 20 andmaintained centred inside the tubular body by a clamp with fluid dynamicspoke 18, an outlet nozzle adjustable in position and opening 16, amotorised system 12, 14, 24 (e.g. an electrical stepper motor) suitableto allow the displacement and the adjustment of said outlet nozzle 16 bymeans of the pinion 13 and the cogwheel 15, a system with cables orlevers or pistons or telescopic arms (not shown) suitable to orient thedirection and the slant of the device by means of the guide of thetubular chamber 1, 1′ mounted on the joint 22, 8, then of the jet 6, todrive the changes of course and attitude of the boat (FIG. 3).

The new polymer body hydrodynamic shaped as tapered pinecone or onion 17has shape and volume variable through an internal hole 17″ which swellsout by means of a pneumatic or hydraulic circuit 17″, able to swell orcontract changing its shape and volume to obtain a further controlelement together or without the need of a restrictor (FIG. 4).

Similarly the support ring nut 18 can be carried out as wing section oraerodynamic profile 18″ and be mobile in translation 18′ from a point ofmaximum excursion to a point of minimum excursion inside the chamber 1′,its displacement 18′ determining the change and the control of a numberof parameters, like for instance shape and dimension of the flowsections, speed, pressure drops by friction, density of the fluid and soon, that contribute to the further, alternatively or concurrently,control and optimisation of the jet (FIG. 5).

The jet 6 of the pumped 3 and conveyed 2, 9, 1′ fluid is in this waycontrolled by the device of the invention which allows to change itscharacteristics of speed and density as one likes, to alter the fluidwith the injection of another fluid into the duct 2 or into the chamber1′, that precede the mobile nozzle 16 which releases said jet, suitableto change the flow characteristics and to allow the mix of the fluidwith a gas, which in this case is the exhaust of the internal combustionengine which drives the pump 4, or alternatively compressed air, andfinally the undoubted innovation which breaks definitely with tradition,the fact that the substantially elaborated flow is ejected above thewater surface 10 with slant and direction controlled and adjusted as onelikes 8. To come to the point this invention can replace or succeed allthe traditional water-jets for boat propulsion, because it allows forthe first time to change the jet characteristics, to alter the flow, toobtain more effectiveness in the propulsion, to obtain considerableincrease of speed for the same used power.

Interacting through the nozzles injecting the engine exhaust orcompressed air and adjusting the geometry of the chamber 1′ by means ofthe electrical stepper motor 12, 13, it results not only the variationof the main characteristics of the jet 6 like speed and density, butalso power and angle of incidence, with increase of the kinetic energyof the jet itself.

The device subject of this invention ensures the boat besides the bestperformances already mentioned, a neutral progress of the movementalways in horizontal position, more comfort, more angle of incidence bythe changes of direction, saving of power, saving of fuel, alladvantages that of course were up to now not found in the previous stateof the technique because in the traditional water-jet it is not possibleto intervene neither to control nor to alter the hydraulic jet. Allthese things are on the contrary achievable by the device subject ofthis invention. The subject of the invention conceived and tested by theapplicant at first sight characterises itself mainly because the jet 6happens above the water surface 10 few centimetres above the water-line10 of the boat 5, 11, and precisely it happens from the top downwards indiagonal with an adjustable slant 8 at will. Further analysing theachieved results we can mention the fact that utilising this device thewake of the boat is cleaner and the turbulent foamy part is no longertied to the stem but it is at a distance of a few metres, in fact, bythe implementation of the invention it is possible to noticeably improvealso the fluid dynamics of the boat. Many further advantages andimprovements can be achieved by the use of the invention; the device canbe carried out of any metal or plastic or composite provided that it issuitable and complies with the technical mechanic requirements peculiarto the intended use.

The water-jet control device described above is finally characterised bythe fact that by means of it, veers more precise, cleaner und sharpercan be achieved with less wasted power; in fact by the traditionalwater-jets to do a veer the rudder damp the jet 6 taking power andincisiveness from the jet itself, inducing a noticeable loss of speed,while by the device, subject of this invention, the veer is alwayscarried out with the full jet 6 available, without the need of anadditional rudder and without damping, without taking or wasting powerand incisiveness, simply because the jet is not diverted by othermembers, but it is oriented by the joint 8 by means of dedicatedtelescopic arms (here not shown in the tables), that allow thedisplacement in all the direction of the tubular body 1 of the device,in fact thanks to this the jet can be fully directed without beingdamped.

The mechanical fluid dynamic jet device for the propulsion and thecontrol of the hydrodynamic flow in the water-jet propelled boats findsalso used in the hydrodynamic guidance and control in the boats when itis symmetrically arranged in a given number of couples on the lateralwalls of the hull to optimise the auxiliary manoeuvres in harbour, saidnozzles being fed by hydraulic pumps through shutters driven byelectrovalves and controlled by joystick.

The device of the invention finds also use to optimise the traditionalsystem of prow propellers and auxiliary propellers for the manoeuvres inharbour, sailing and docking of the boats. (FIGS. 6, 7).

An installation with four water-jets, one port and one starboard prow,likewise two stern water-jets, results much more easy and functionalthan any system with traditional electric motor, because it makes use offour holes made on the hull, one for each device, positioned on thewater surface, avoiding the complex and expensive work to installelectric motors with auxiliary propeller.

The system configured in this way beside the water-jets that are linkedthrough ducts to a single hydraulic pump with intake from the sea (alsothis extremely simple) adopts four electrically driven valves one foreach jet controlled by a joystick.

By the installation with one couple, two couples or more couples ofwater-jets 1, they are linked through ducts 30, 30′, with interposedshutters 27, 27′ driven by electrovalves 28, 28′, to a single hydraulicpump for each couple 29, 29′ with intake from the sea (also thisextremely simple) and adopt electrically driven valves 28, 28′, one foreach jet, controlled by a joystick, for the differential control of theflow of the said water-jets (FIGS. 6,7).

The system is very reliable, assures perfect manoeuvring with immediateand precise response, but above all it will be promoted because of itsinstallation simplicity, reliability and cost on the new boats as wellas on the second-hand ones.

The carrying out of the installation with four water-jets (with thedevice of the invention) was satisfactory tested on a 24-metersuper-yacht.

The mechanical fluid dynamic jet device for the propulsion and thecontrol of the hydrodynamic flow in the water-jet propelled boats findsalso used in the hydrodynamic guidance and control in the boats when itis symmetrically arranged in a given number of couples on the lateralwalls of the hull to optimise the auxiliary manoeuvres in harbour, saidnozzles being fed by hydraulic pumps through shutters driven byelectrovalves and controlled by joystick.

The mechanical fluid dynamic jet device find particularly use for thecontrol of the hydrodynamic flow in the propulsion and the manoeuvre ofthe water-jet propelled boats or crafts.

The system finds also use to optimise the traditional system of prowpropellers and auxiliary propellers for the manoeuvres in harbour,sailing and docking.

The device subject of this invention can have many forms and variationsrelevant to the geometry, the fluid dynamics, the materials, the detailsor particulars here not described but not for this excluded by the ambitof protection of such invention.

It finds particular use by the propulsion and control of thehydrodynamic flow in the water-jet propelled boats or crafts.

Furthermore said device allows retrofit actions in the boats of theknown technique, because can be easily embodied also on the boats thathave a traditional water-jet.

1) Mechanical fluid dynamic jet device for the propulsion and control ofthe hydrodynamic flow in the water-jet propelled boats, includingconveying ducts of the fluid (2, 9), a tubular mean (1) with variablegeometry and variable internal volume, a body (17) centred inside saidtubular mean by means of a wing-shaped ring or support nut (18) withspokes or fluid dynamic blades, an adjustable nozzle (16) to eject thefluid, one or more gas injectors (21), and means (8, 22) to change thedirection and the slant of the jet (6), characterised by the fact thatthe change of the volume of the chamber (1′) inside the tubular mean (1)for the control of the flow is obtained by displacement and opening ofthe adjustable nozzle (16) to change said internal volume (1′), withoutthe need to change the shape and geometry of said nozzle (16) (FIG. 3).2) Mechanical fluid dynamic jet device for the propulsion and control ofthe hydrodynamic flow in the water-jet propelled boats, according theclaim 1, characterised by the fact that the movement of the nozzle (16)for the adjustment of the volume of the chamber (1′) inside the tubularmean (1) is carried out by a motorised system including a motor (12, 14,24), like an electrical stepper motor, and by a gearbox, pinion andcogwheel (13, 15), suitable to displace, adjust and restrict said nozzle(16) from a minimum to a maximum opening position for the variation ofthe kinetic energy of the jet (6) itself. (FIG. 3). 3) Mechanical fluiddynamic jet device for the propulsion and control of the hydrodynamicflow in the water-jet propelled boats, according to claim 1 or 2,characterised by the fact that the tapered pinecone or onion-shaped body(17) to drive and control the flow is made of deformable plasticmaterial and has a hole (17′) linked to a hydraulic circuit (17″) to befilled by a fluid to change its volume and obtain a further adjustableelement to control the hydrodynamic flow (FIG. 4). 4) Mechanical fluiddynamic jet device for the propulsion and control of the hydrodynamicflow in the water-jet propelled boats, according to any one of theprevious claims, characterised by the fact the ring or nut (18), onwhich the pinecone or onion-shaped body is mounted and centred (19, 20,23) for guidance and control of the hydrodynamic flow inside the tubularmean (1), has a wing section or an aerodynamic profile (18″) and canmove (18′) along the axis of the said body (17) from a minimum to amaximum point, to guarantee a depression at its centre and to direct thegas or air on the said onion-shaped tubular element, to determine afurther adjustable element to change the parameters of the flow (FIG.5). 5) Mechanical fluid dynamic jet device for the propulsion andcontrol of the hydrodynamic flow in the water-jet propelled boats,according to any one of the previous claims, characterised by the factthat the injectors (21) are placed and arranged at the centre of thering (18) with wing section (18″) to force the gas to lap only on thesurface of the pinecone (17) without disperse on the chamber (1′). 6)Mechanical fluid dynamic jet device for the propulsion and control ofthe hydrodynamic flow in the water-jet propelled boats, according to anyone of the previous claims, characterised by the fact that the jet (6),besides the possibility of a release underwater like the traditionalwater-jets, can be also released outside the water above the watersurface (10), like a jet engine or water-jet, said option resulting moreeffective and more appreciable in terms of better performances. 7) Useof the mechanical fluid dynamic jet device for the propulsion andcontrol of the hydrodynamic flow in the water-jet propelled boats,according to any one of the previous claims, characterised by the factthat it (1) is symmetrically arranged in a determined number of coupleson the lateral walls of the hull to optimise the auxiliary manoeuvres inharbour, said water-jets (1) being fed by hydraulic pumps (29, 29′)through ducts (30, 30′) and shutters (27, 27′) driven by electrovalves(28, 28′) and controlled by joystick (FIGS. 6, 7). 8) Use of themechanical fluid dynamic jet device, according to any one of theprevious claims, for the control of the hydrodynamic flow in thepropulsion and in the manoeuvre of the water-jet propelled boats orcrafts. 9) Use of the mechanical fluid dynamic jet device for thepropulsion and control of the hydrodynamic flow in the water-jetpropelled boats, according to any one of the previous claims, for thecontrol of the hydrodynamic flow in the propulsion and in the manoeuvreof the water-jet propelled boats or crafts, as a retrofit of easyembodiment to be installed also on the boats that have a water-jet ormanoeuvring propellers of traditional type.